You’re more than welcome to contact a host at any time, whether you’re booking a home, experience or service.
Unless you’ve found an Instant Book listing, you’ll have to ask that the host accept your request to book. At the Confirm and pay stage of your request, you’ll need to include a brief message about why you’re travelling and when you’ll check in.
If you’re booking a home, just be careful not to send more than one trip request for the same dates to ensure you don’t end up double booked.
Most hosts respond within a few hours, but time zones and lack of internet access might slow things down.